A core file or core dump is a file that records the memory image of a running process and its process status (register values etc.). Its primary use is post-mortem debugging of a program that crashed while it ran outside a debugger. A program that crashes automatically produces a core file, unless this feature is disabled by the user. See Files, for information on invoking GDB in the post-mortem debugging mode.
Occasionally, you may wish to produce a core file of the program you are debugging in order to preserve a snapshot of its state. GDB has a special command for that.
Produce a core dump of the inferior process. The optional argument file specifies the file name where to put the core dump. If not specified, the file name defaults to core.pid, where pid is the inferior process ID.
Note that this command is implemented only for some systems (as of this writing, GNU/Linux, FreeBSD, Solaris, and S390).